This analytical core will be housed at Lamont-Doherty Earth Observatory (LDEO) and will provide elemental and Pb-isotopic measurements on samples of waters, soils, sediments, sludges, aerosol filters, paints and dust. These measurements are designed to establish the sources of lead (and other heavy metal) contamination in the N.Y.C. environment. Samples from the following projects will be analyzed at LDEO: 1. Human Lead Exposure and Environmental Contamination/Recontamination under N.Y.C. Bridges. 2. Sources and Pathways of Urban Heavy Metal Exposure Using Elemental and Isotopic Composition of Environmental Samples. 3. Sources and Pathways of Chlorinated Hydrocarbon Exposure Derived from New York City Water and Air. In order to make these measurements we will take advantage of Inductively-Coupled Plasma Mass Spectrometry, Thermal Ionization Mass Spectrometry, and Gamma-Ray Spectrometry facilities, as well as chemical preparation laboratories at LDEO.